Photothermographic film generally comprises a base material, such as a thin polymer or paper, typically coated on one side with an emulsion of heat sensitive materials. Once the film has been subjected to photostimulation, via the laser of a laser imager for example, a thermal processor is employed to develop the resulting latent image through application of heat to the film. In general, a thermal processor raises the base material and emulsion to an optimal development temperature and holds the film at the development temperature for a required time period to develop the image. However, in order to provide optimal and consistent quality in developed images, a thermal processor must perform this heating process smoothly and consistently within a single film and between subsequent films. Additionally, in order to ensure that chemical reactions proceed correctly in the emulsion and to increase film throughput, the thermal processor must accomplish this temperature rise as quickly as possible without causing distortions or wrinkling of the base material.
Two primary types of thermal processors, drum processors and flatbed processors, have been developed by the industry for thermally developing photothermographic film. Drum processors are characterized by a rotating heated drum having a series of pressure rollers positioned around a segment of the drum's surface. During development, the pressure rollers generally hold the emulsion-side of the film in contact with heated drum. However, as some types of photothermographic film are heated, their emulsions produce gaseous byproducts, particularly while the film is at the development temperature. While drum processors heat the film quickly and smoothly, the gaseous byproducts can sometimes be trapped between the film and the drum and condense on the drum's surface. Over time, such contaminants can accumulate on the drum's surface and cause visual artifacts in the developed image. Consequently, drum processors require regular and costly maintenance to clean the accumulated contaminants from the drum.
Also, the drum's size (i.e. diameter) is dependent on the film's development time and the desired throughput of the processor, wherein increasing the processor's throughput while holding the development time constant requires an increase in the drum's size. As a result, the throughput of a drum processor is limited as the required drum size quickly becomes impractical as the throughput is increased.
Flatbed processors are characterized by a series of spaced rollers that convey the photothermographic along a typically horizontal path through a heated oven. One advantage of flatbed processors is that the gaseous byproducts produced by the film during development can be more easily captured and conveyed away from the processor as compared to drum processors. Additionally, flatbed processors generally heat the photothermographic film more slowly than drum processors, enabling the film's base material to expand without wrinkling or distorting. However, the slower rate of heating requires a longer heated path and oven, resulting in the flatbed processor having a larger physical size relative to a drum processor.
Thus, there is a need for an improved thermal processor that reduces the above described problems associated with conventional thermal processors.